This invention relates to a novel cordless vehicle tire and method for its manufacture.
Conventional vehicle tires containing cords are notoriously non-uniform and almost invariably require balancing when mounted in order to provide a smooth ride and even tire wear. A tire which is uniform to a greater extent than conventional tires in weight distribution would represent a substantial advance in eliminating the expense of balancing and improving smoothness of operation. Prior attempts to produce such tires have been unsuccessful-- tires presently available commercially invariably require balancing, and perfect balancing is a practical impossibility.
Additional problems posed by conventional tires are that in order to obtain adequate rubber-to-cord adhesion, cords must be coated with one or more layers of complex adhesive compositions which requires the use of costly equipment. The cords in conventional tires also impose problems caused by factors such as stiffness, the tendency of polyester cords to degrade from attack by some rubber curing agent by-products and nylon's "thumping" caused by set occurring after the tire has been kept under load in one position. Furthermore, the elastomeric matrix of a conventional tire carcass built from layers of rubberized plies tends to be non-homogeneous which leads to a non-uniform cure and potential weak spots in the tire carcass.
Ease and rapidity of manufacture are important considerations in making tires. Prior to this invention it was necessary to cure tires made of polyurethane for relatively lengthy periods. The present invention provides a tire which permits curing of the polyurethane, generally, in less than about 2-6 minutes, while, at the same time, premature curing is quite easily avoided.